Internal combustion engines of the initially mentioned type are known. The supercharger assigned to the internal combustion engine is used to compress the air supplied to the internal combustion engine before it enters the combustion chambers. This measure increases the amount of air available for combustion or the air throughput, therefore the air mass flow per unit of time, compared to an internal combustion engine without a supercharger. The output of the internal combustion engine can be markedly increased by the larger amount of air available for combustion. The compression of the supplied medium, especially air, however, causes a temperature rise. It can be ascribed first of all directly to the compression, but the compressor side of a supercharger heats up during operation, for example, due to friction effects or the addition of heat from the heated medium or the turbine side, so that at low compression ratios the temperature of the medium is further increased.
This temperature increase of the medium is undesirable since it reduces the efficiency of the internal combustion engine. On the one hand, with rising temperature the air density decreases so that at the same combustion chamber volume the air mass available for combustion decreases, on the other hand the efficiency of the thermodynamic circulation process of the internal combustion engine drops due to the rising entry temperature. To avoid these disadvantages, the charging air which is supplied to the internal combustion engine and which originates from the supercharger can be cooled down to a lower temperature level using an intercooler. The intercooler is conventionally connected to a cooling circuit and is thus used as a heat exchanger between a cooling fluid and the charging air. In order to be able to control the charging pressure on the internal combustion engine there is a pressure setting device. By way of this pressure setting device already compressed air can travel back into the region upstream from the supercharger so that there is circulation. Especially at low outside temperatures it can happen that large amounts of cold air travel directly into the intercooler and ice forms in the intercooler. This raises the pressure loss between the supercharger and engine and thus reduces the efficiency of the supercharger and of the internal combustion engine. This can be the case especially during implementation of crankcase ventilation. The moisture contained in the air in this case can condense on the intercooler, whereupon ice can form.
The object of this invention is to make available a process for operating an internal combustion engine in order to be able to easily detect such an icing state of the intercooler and eliminate it by countermeasures.